In the fabrication of semiconductor integrated circuits, metal conductor lines are used to interconnect the multiple components in device circuits on a semiconductor wafer. A general process used in the deposition of metal conductor line patterns on semiconductor wafers includes deposition of a conducting layer on the silicon wafer substrate; formation of a photoresist or other mask such as titanium oxide or silicon oxide, in the form of the desired metal conductor line pattern, using standard lithographic techniques; subjecting the wafer substrate to a dry etching process to remove the conducting layer from the areas not covered by the mask, thereby leaving the metal layer in the form of the masked conductor line pattern; and removing the mask layer typically using reactive plasma and chlorine gas, thereby exposing the top surface of the metal conductor lines. Typically, multiple alternating layers of electrically conductive and insulative materials are sequentially deposited on the wafer substrate, and conductive layers at different levels on the wafer may be electrically connected to each other by etching vias, or openings, in the insulative layers and filling the vias using aluminum, tungsten or other metal to establish electrical connection between the conductive layers.
Deposition of conductive layers on the wafer substrate can be carried out using any of a variety of techniques. These include oxidation, LPCVD (low-pressure chemical vapor deposition), APCVD (atmospheric-pressure chemical vapor deposition), and PECVD (plasma-enhanced chemical vapor deposition). In general, chemical vapor deposition involves reacting vapor-phase chemicals that contain the required deposition constituents with each other to form a nonvolatile film on the wafer substrate. Chemical vapor deposition is the most widely-used method of depositing films on wafer substrates in the fabrication of integrated circuits on the substrates.
Due to the ever-decreasing size of semiconductor components and the ever-increasing density of integrated circuits on a wafer, the complexity of interconnecting the components in the circuits requires that the fabrication processes used to define the metal conductor line interconnect patterns be subjected to precise dimensional control. Advances in lithography and masking techniques and dry etching processes, such as RIE (Reactive Ion Etching) and other plasma etching processes, allow production of conducting patterns with widths and spacings in the submicron range. Electrodeposition or electroplating of metals on wafer substrates has recently been identified as a promising technique for depositing conductive layers on the substrates in the manufacture of integrated circuits and flat panel displays. Such electrodeposition processes have been used to achieve deposition of the copper or other metal layer with a smooth, level or uniform top surface. Consequently, much effort is currently focused on the design of electroplating hardware and chemistry to achieve high-quality films or layers which are uniform across the entire surface of the substrates and which are capable of filling or conforming to very small device features. Copper has been found to be particularly advantageous as an electroplating metal.
Electroplated copper provides several advantages over electroplated aluminum when used in integrated circuit (IC) applications. Copper is less electrically resistive than aluminum and is thus capable of higher frequencies of operation. Furthermore, copper is more resistant to electromigration (EM) than is aluminum. This provides an overall enhancement in the reliability of semiconductor devices because circuits which have higher current densities and/or lower resistance to EM have a tendency to develop voids or open circuits in their metallic interconnects. These voids or open circuits may cause device failure or burn-in.
Electrochemical mechanical deposition (ECMD) is a technique which has been developed recently for plating a conductive material on a semiconductor wafer or workpiece surface. One goal of ECMD is to uniformly fill holes and trenches on the wafer/workpiece surface with the conductive material while maintaining the planarity of the surface. A typical conventional ECMD system is shown schematically in FIG. 1. The ECMD system 10 includes a anode assembly 12, having a top plate 14 removably mounted on a bottom plate 16. A typically copper anode 18 is contained in the anode assembly 12 with a supply of electrolyte solution (not shown). An anode pad 20, typically having multiple pores 21 extending therethrough, is provided on the top plate 14. A semiconductor wafer 24 is positioned face-down on the anode pad 20, with the backside 26 of the wafer 24 facing upwardly.
During the ECMD process, a conductive material, such as copper from the typically copper anode 18, is applied in holes, trenches and/or other desired areas on the wafer 24 using an electrolyte solution (not shown) in the anode assembly 12. The electrolyte solution flows from the anode 18 and through the top plate 14 and the pores 21 of the anode pad 20, respectively, where the copper cations from the anode 18 are reduced to form a copper deposit on the wafer 24. One of the problems inherent in the conventional ECMD system 10 is that particles 22 frequently precipitate on the top surface of the anode pad 20. These particles 22 tend to scratch or peel the wafer 24 upon movement of the wafer 24 on the anode pad 20 during the ECMD process, as well as upon initial positioning or eventual removal of the wafer 24 on or from the anode pad 20.
Accordingly, an object of the present invention is to provide an apparatus for removing particles from an anode pad in an electroplating system.
Another object of the present invention is to provide a method for removing particles from an anode pad in an ECMD system.
Another object of the present invention is to provide an apparatus for preventing or minimizing inadvertent scratching or peeling of semiconductor wafers in an ECMD system.
Still another object of the present invention is to provide an apparatus for prolonging the lifetime of an anode pad in an ECMD system.
Yet another object of the present invention is to provide an apparatus which dislodges and removes particles from an anode pad after an ECMD process.
A still further object of the present invention is to provide an apparatus which utilizes a vacuum force alone or in combination with a scrubbing action to dislodge and remove particles from an anode pad after an ECMD process.
Yet another object of the present invention is to provide an in-situ apparatus for low-pressure conditioning of an anode pad in an ECMD system and dislodging and removing particles from the anode pad.
Another object of the present invention is to provide an insitu apparatus which utilizes a vacuum-induced high-pressure electrolyte spray to remove particles from an anode pad in an ECMD system.
A still further object of the present invention is to provide an apparatus for maintaining an electrolyte solution for an ECMD system in a substantially low-particle, clean condition.
Yet another object of the present invention is to provide an apparatus which has no effect on the throughput of semiconductor wafers processed in a facility.